Characterization of surface functional groups present on laboratory-generated and ambient aerosol particles by means of heterogeneous titration reactions

A Knudsen flow reactor has been used to quantify surface functional groups on aerosols collected in the field. This technique is based on a heterogeneous titration reaction between a probe gas and a specific functional group on the particle surface. In the first part of this work, the reactivity of different probe gases on laboratory-generated aerosols (limonene SOA, Pb(NO3)2, Cd(NO3)2) and diesel reference soot (SRM 2975) has been studied. Five probe gases have been selected for the quantitative determination of important functional groups: N(CH3)3 (for the titration of acidic sites), NH2OH (for carbonyl functions), CF3COOH and HCl (for basic sites of different strength), and O3 (for oxidizable groups). The second part describes a field campaign that has been undertaken in several bus depots in Switzerland, where ambient fine and ultrafine particles were collected on suitable filters and quantitatively investigated using the Knudsen flow reactor. Results point to important differences in the surface reactivity of ambient particles, depending on the sampling site and season. The particle surface appears to be multi-functional, with the simultaneous presence of antagonistic functional groups which do not undergo internal chemical reactions, such as acid-base neutralization. Results also indicate that the surface of ambient particles was characterized by a high density of carbonyl functions (reactivity towards NH2OH probe in the range 0.26-6 formal molecular monolayers) and a low density of acidic sites (reactivity towards N(CH3)3 probe in the range 0.01-0.20 formal molecular monolayer). Kinetic parameters point to fast redox reactions (uptake coefficient ?0>10-3 for O3 probe) and slow acid-base reactions (?0<10-4 for N(CH3)3 probe) on the particle surface. [Authors]

Behavioural queueing : cellular automata and a laboratory experiment

Dans cette thèse, nous étudions les aspects comportementaux d'agents qui interagissent dans des systèmes de files d'attente à l'aide de modèles de simulation et de méthodologies expérimentales. Chaque période les clients doivent choisir un prestataire de servivce. L'objectif est d'analyser l'impact des décisions des clients et des prestataires sur la formation des files d'attente. Dans un premier cas nous considérons des clients ayant un certain degré d'aversion au risque. Sur la base de leur perception de l'attente moyenne et de la variabilité de cette attente, ils forment une estimation de la limite supérieure de l'attente chez chacun des prestataires. Chaque période, ils choisissent le prestataire pour lequel cette estimation est la plus basse. Nos résultats indiquent qu'il n'y a pas de relation monotone entre le degré d'aversion au risque et la performance globale. En effet, une population de clients ayant un degré d'aversion au risque intermédiaire encoure généralement une attente moyenne plus élevée qu'une population d'agents indifférents au risque ou très averses au risque. Ensuite, nous incorporons les décisions des prestataires en leur permettant d'ajuster leur capacité de service sur la base de leur perception de la fréquence moyenne d'arrivées. Les résultats montrent que le comportement des clients et les décisions des prestataires présentent une forte "dépendance au sentier". En outre, nous montrons que les décisions des prestataires font converger l'attente moyenne pondérée vers l'attente de référence du marché. Finalement, une expérience de laboratoire dans laquelle des sujets jouent le rôle de prestataire de service nous a permis de conclure que les délais d'installation et de démantèlement de capacité affectent de manière significative la performance et les décisions des sujets. En particulier, les décisions du prestataire, sont influencées par ses commandes en carnet, sa capacité de service actuellement disponible et les décisions d'ajustement de capacité qu'il a prises, mais pas encore implémentées. - Queuing is a fact of life that we witness daily. We all have had the experience of waiting in line for some reason and we also know that it is an annoying situation. As the adage says "time is money"; this is perhaps the best way of stating what queuing problems mean for customers. Human beings are not very tolerant, but they are even less so when having to wait in line for service. Banks, roads, post offices and restaurants are just some examples where people must wait for service. Studies of queuing phenomena have typically addressed the optimisation of performance measures (e.g. average waiting time, queue length and server utilisation rates) and the analysis of equilibrium solutions. The individual behaviour of the agents involved in queueing systems and their decision making process have received little attention. Although this work has been useful to improve the efficiency of many queueing systems, or to design new processes in social and physical systems, it has only provided us with a limited ability to explain the behaviour observed in many real queues. In this dissertation we differ from this traditional research by analysing how the agents involved in the system make decisions instead of focusing on optimising performance measures or analysing an equilibrium solution. This dissertation builds on and extends the framework proposed by van Ackere and Larsen (2004) and van Ackere et al. (2010). We focus on studying behavioural aspects in queueing systems and incorporate this still underdeveloped framework into the operations management field. In the first chapter of this thesis we provide a general introduction to the area, as well as an overview of the results. In Chapters 2 and 3, we use Cellular Automata (CA) to model service systems where captive interacting customers must decide each period which facility to join for service. They base this decision on their expectations of sojourn times. Each period, customers use new information (their most recent experience and that of their best performing neighbour) to form expectations of sojourn time at the different facilities. Customers update their expectations using an adaptive expectations process to combine their memory and their new information. We label "conservative" those customers who give more weight to their memory than to the xiv Summary new information. In contrast, when they give more weight to new information, we call them "reactive". In Chapter 2, we consider customers with different degree of risk-aversion who take into account uncertainty. They choose which facility to join based on an estimated upper-bound of the sojourn time which they compute using their perceptions of the average sojourn time and the level of uncertainty. We assume the same exogenous service capacity for all facilities, which remains constant throughout. We first analyse the collective behaviour generated by the customers' decisions. We show that the system achieves low weighted average sojourn times when the collective behaviour results in neighbourhoods of customers loyal to a facility and the customers are approximately equally split among all facilities. The lowest weighted average sojourn time is achieved when exactly the same number of customers patronises each facility, implying that they do not wish to switch facility. In this case, the system has achieved the Nash equilibrium. We show that there is a non-monotonic relationship between the degree of risk-aversion and system performance. Customers with an intermediate degree of riskaversion typically achieve higher sojourn times; in particular they rarely achieve the Nash equilibrium. Risk-neutral customers have the highest probability of achieving the Nash Equilibrium. Chapter 3 considers a service system similar to the previous one but with risk-neutral customers, and relaxes the assumption of exogenous service rates. In this sense, we model a queueing system with endogenous service rates by enabling managers to adjust the service capacity of the facilities. We assume that managers do so based on their perceptions of the arrival rates and use the same principle of adaptive expectations to model these perceptions. We consider service systems in which the managers' decisions take time to be implemented. Managers are characterised by a profile which is determined by the speed at which they update their perceptions, the speed at which they take decisions, and how coherent they are when accounting for their previous decisions still to be implemented when taking their next decision. We find that the managers' decisions exhibit a strong path-dependence: owing to the initial conditions of the model, the facilities of managers with identical profiles can evolve completely differently. In some cases the system becomes "locked-in" into a monopoly or duopoly situation. The competition between managers causes the weighted average sojourn time of the system to converge to the exogenous benchmark value which they use to estimate their desired capacity. Concerning the managers' profile, we found that the more conservative Summary xv a manager is regarding new information, the larger the market share his facility achieves. Additionally, the faster he takes decisions, the higher the probability that he achieves a monopoly position. In Chapter 4 we consider a one-server queueing system with non-captive customers. We carry out an experiment aimed at analysing the way human subjects, taking on the role of the manager, take decisions in a laboratory regarding the capacity of a service facility. We adapt the model proposed by van Ackere et al (2010). This model relaxes the assumption of a captive market and allows current customers to decide whether or not to use the facility. Additionally the facility also has potential customers who currently do not patronise it, but might consider doing so in the future. We identify three groups of subjects whose decisions cause similar behavioural patterns. These groups are labelled: gradual investors, lumpy investors, and random investor. Using an autocorrelation analysis of the subjects' decisions, we illustrate that these decisions are positively correlated to the decisions taken one period early. Subsequently we formulate a heuristic to model the decision rule considered by subjects in the laboratory. We found that this decision rule fits very well for those subjects who gradually adjust capacity, but it does not capture the behaviour of the subjects of the other two groups. In Chapter 5 we summarise the results and provide suggestions for further work. Our main contribution is the use of simulation and experimental methodologies to explain the collective behaviour generated by customers' and managers' decisions in queueing systems as well as the analysis of the individual behaviour of these agents. In this way, we differ from the typical literature related to queueing systems which focuses on optimising performance measures and the analysis of equilibrium solutions. Our work can be seen as a first step towards understanding the interaction between customer behaviour and the capacity adjustment process in queueing systems. This framework is still in its early stages and accordingly there is a large potential for further work that spans several research topics. Interesting extensions to this work include incorporating other characteristics of queueing systems which affect the customers' experience (e.g. balking, reneging and jockeying); providing customers and managers with additional information to take their decisions (e.g. service price, quality, customers' profile); analysing different decision rules and studying other characteristics which determine the profile of customers and managers.

Needs, expectations, and concerns of medical students regarding end-of-life issues before the introduction of a mandatory undergraduate palliative care curriculum.

BACKGROUND: In the past, implementation of effective palliative care curricula has emerged as a priority in medical education. In order to gain insight into medical students' needs and expectations, we conducted a survey before mandatory palliative care education was introduced in our faculty. METHODS: Seven hundred nine students answered a questionnaire mainly consisting of numeric rating scales (0-10). RESULTS: Participants attributed a high importance to palliative care for their future professional life (mean, 7.51 ± 2.2). For most students, symptom control was crucial (7.72 ± 2.2). However, even higher importance was assigned to ethical and legal issues (8.16 ± 1.9). "Self-reflection regarding their own role as a physician caring for the terminally ill along with psychological support" was also regarded as highly important (7.25 ± 2.4). Most students were moderately concerned at the prospect of being confronted with suffering and death (5.13 ± 2.4). This emotional distress was rated significantly higher by female students (5.4 ± 2.4 versus 4.6 ± 2.4; p < 0.001). Seventeen percent of all students rated their distress as being 7 of 10 or higher, which indicates a considerable psychological strain in terms of dealing with end-of-life issues in the future. Professional or personal experience with terminally ill persons lowered these anxieties significantly (4.99 ± 2.34 versus 5.47 ± 2.5, p < 0.05). CONCLUSIONS: Medical students stated a remarkably high interest in learning palliative care competencies. Responding to their specific concerns and needs-especially with regard to the acquisition of emotional coping skills-may be key for the development of successful palliative care curricula.

Use of active personal dosemeters in interventional radiology and cardiology: Tests in laboratory conditions and recommendations - ORAMED project

Active personal dosemeters (APD) have been found to be very efficient tools to reduce occupational doses in many applications of ionizing radiation. In order to be used in interventional radiology and cardiology (IR/IC), APDs should be able to measure low energy photons and pulsed radiation with relatively high instantaneous personal dose equivalent rates. A study concerning the optimization of the use of APDs in IR/IC was performed in the framework of the ORAMED project, a Collaborative Project (2008-2011) supported by the European Commission within its 7th Framework Program. In particular, eight commercial APDs were tested in continuous and pulsed X-ray fields delivered by calibration laboratories in order to evaluate their performances. Most of APDs provide a response in pulsed mode more or less affected by the personal dose equivalent rate, which means they could be used in routine monitoring provided that correction factors are introduced. These results emphasize the importance of adding tests in pulsed mode in type-test procedures for APDs. Some general recommendations are proposed in the end of this paper for the selection and use of APDs at IR/IC workplaces.

Spectral induced polarization: Laboratory measurements on sandy quartz samples of varied pore characteristics

Understanding the influence of pore space characteristics on the hydraulic conductivity and spectral induced polarization (SIP) response is critical for establishing relationships between the electrical and hydrological properties of surficial sedimentary deposits. Here, we present the results of laboratory SIP measurements on saturated quartz samples with granulometric characteristics ranging from fine sand to fine gravel. We alter the pore characteristics using three principal methods: (i) variation of the grain sizes, (ii) changing the degree of compaction, and (iii) changing the level of sorting. We then examine how these changes affect both the SIP response and the hydraulic conductivity. In general, the results indicate a clear connection between the applied changes in pore characteristics and the SIP response. In particular, we observe a systematic correlation between the hydraulic conductivity and the relaxation time of the Cole-Cole model describing the observed SIP effect for the whole range of considered grain sizes.

Fitness cost and impaired survival in penicillin-resistant Streptococcus gordonii isolates selected in the laboratory.

Cycling of Streptococcus gordonii (115 times) with penicillin resulted in a MIC increase of more than 100-fold, from 0.008 to 2 microg/ml. The 2-microg/ml MIC maximum was already reached after 36 passages but resulted in impaired fitness. Although the MIC did not increase further, fitness was partially recovered during the 79 additional cycles.

Improving breast cancer education: the case of an evolving multidisciplinary module for undergraduate medical students (lausanne medical school, 1993-2008).

Breast cancer is a public health issue in numerous countries. Multidisciplinary collaboration is required for patient care, research, and also education of future physicians. This paper uses Kern's framework for curriculum design to demonstrate how a breast diseases module for undergraduate medical students created in 1993 evolved over 15 years. The main outcomes of program refinements were better integrated course content, the development of electronic course documents, and implementation of computer-aided small group learning. A main future challenge is to further develop efficient instructional strategies in line with well-defined learning needs for undergraduate students.

Cellules gliales et douleur chronique: du laboratoire a l'espoir clinique [Glial cells and chronic pain: from the laboratory to clinical hope].

Despite their high prevalence, associated disability and seemingly rich pharmacopeia, the various forms of chronic pain remain frequently intractable. The past decade witnessed the rise of a concept stating that non-neuronal cells of the central nervous system, astrocytes and microglia, are crucial elements in pathological pain. This review gathers and summarizes the experimental data underpinning this theory in animal models and addresses their pertinence in humans. The potential opportunities and constraints of glial inhibition are exposed and compared to more moderate strategies of selective modulation. This therapeutic hope is particularly highlighted in our discussion of the first completed clinical trials employing glial inhibitors in the treatment of chronic pain.

New developments in laboratory monitoring of HIV-1 infection.

The laboratory tests currently available to the clinician for day-to-day management of HIV infection are generally limited to the measurement of the viral load and of the CD4 cell count. More recently, analysis of drug resistance and of plasma drug levels have been added to the monitoring armamentarium. There are, however, numerous other techniques currently available to researchers that may in the future be incorporated into clinical routine. These include the analysis of human and viral genetic determinants of disease evolution, detailed analyses of immune recovery and reserve, pharmacogenetic determinants of treatment response, and toxicity. These approaches may in the future provide highly individualized disease management.

Clinical and laboratory predictors of imported malaria in an outpatient setting: an aid to medical decision making in returning travellers with fever

Si le tableau clinique évoque une malaria et que le résultat des examens parasitologiques n?est pas disponible ou est négatif, le praticien n?a pas d?information basée sur l?évidence pour savoir s?il doit donner ou non un traitement présomptif. Afin d?identifier les facteurs cliniques et paracliniques prédictifs d?une parasitémie à Plasmodium, nous avons mené une étude prospective chez les voyageurs ou migrants en provenance d?une zone tropicale ou subtropicale et qui consultaient pour de la fièvre. Le questionnaire comprenait 49 items explorant les données démographiques, les caractéristiques du voyage, les éléments de l?anamnèse et de l?examen clinique ainsi que les résultats de laboratoire. 336 sujets avec données complètes ont été recrutés (97 patients atteints de malaria et 239 contrôles avec fièvre et examen parasitologique négatif). L?analyse de régression multivariée a permis d?identifier les facteurs prédictifs de maiaria suivants : prophylaxie inadéquate, sudations, absence de douleur abdominale, température )38"C, mauvais état général, splénomégalie, compte leucocytaire (1 O x 1 03/L, plaquettes ~ 1 5 0 x l 03/L, taux d?hémoglobine <12 g/dL et éosinophiles (5%. La présence d?une splénomégalie avait le coefficient de probabilité positif pour un diagnostic de malaria le plus élevé (1 3.6) ; venait ensuite la présence d?une thrombopénie (1 1 .O). Dans le contexte de la consultation ambulatoire de la Policlinique Médicale Universitaire (prévalence de malaria de 29%), la probabilité post- test d?avoir un examen parasitologique positif était de 85% pour la splénomégalie et de 82% pour la thrombopénie. Même si le seuil thérapeutique n?est pas absolument défini, il semble raisonnable d?envisager un traitement présomptif lorsque la probabilité post- test est >80%. Si le médecin est réticent à administrer un traitement sans documentation parasitologique, il devrait au moins se retenir d?entreprendre d?autres investigations coûteuses, et plutôt répéter l?examen parasitologique après 12-24 heures.